27.1 Early Concepts of Light In the time of the Greek philosophers, light was perceived in many different ways. Some believed that light consisted of tiny particles which entered the eye; others thought that light traveled from the eye to the object that is looked at. However a man named Empedocles believed that all light traveled in waves. In 1905 Albert Einstein discovered that light is made up of photons, though they are particles, the take the characteristics of waves. Photons – massless bundles of concentrated electromagnetic energy.
27.2 The Speed of Light Originally light was said to immediately travel from one place to another. It wasn’t until the late 17th century that light was found to have a finite speed. Ex: it takes about 8 minutes to travel from the Sun to Earth. Speed of Light = Extra Distance Traveled / Extra Time Measured = 300,000,000km / 1000s =300,000km/s Light-year - the distance light travels in one year.
27.3 Electromagnetic Waves Electromagnetic wave – a wave that is partially magnetic and partially electric Electromagnetic spectrum – includes radio waves, microwaves, and x-rays Infrared – electromagnetic waves of frequencies lower than visible light Ultraviolet – electromagnetic waves of frequencies higher than visible light 27.4 Light and Transparent Materials When light travels through a transparent material, it is absorbed and re-emitted by the atoms that it strikes. Transparent – materials that allow light to pass through in straight lines 27.5 Opaque Materials Opaque – materials that absorb light without reemission and thus allow no light through 27.6 Shadows Ray – Thin beam of light Shadow – formed where light rays cannot reach Umbra – a total shadow Penumbra – a partial shadow
27.7 Polarization Polarization – the aligning vibrations in a transverse wave, usually by filtering out waves of others directions
27.8 Polarized Light and 3-D Viewing
Light
27.1 Early Concepts of LightIn the time of the Greek philosophers, light was perceived in many different ways. Some believed that light consisted of tiny particles which entered the eye; others thought that light traveled from the eye to the object that is looked at. However a man named Empedocles believed that all light traveled in waves. In 1905 Albert Einstein discovered that light is made up of photons, though they are particles, the take the characteristics of waves.
Photons – massless bundles of concentrated electromagnetic energy.
27.2 The Speed of Light
Originally light was said to immediately travel from one place to another. It wasn’t until the late 17th century that light was found to have a finite speed.
Ex: it takes about 8 minutes to travel from the Sun to Earth.
Speed of Light = Extra Distance Traveled / Extra Time Measured
= 300,000,000km / 1000s =300,000km/s
Light-year - the distance light travels in one year.
27.3 Electromagnetic Waves
Electromagnetic wave – a wave that is partially magnetic and partially electric
Electromagnetic spectrum – includes radio waves, microwaves, and x-rays
Infrared – electromagnetic waves of frequencies lower than visible light
Ultraviolet – electromagnetic waves of frequencies higher than visible light
27.4 Light and Transparent Materials
When light travels through a transparent material, it is absorbed and re-emitted by the atoms that it strikes.
Transparent – materials that allow light to pass through in straight lines
27.5 Opaque Materials
Opaque – materials that absorb light without reemission and thus allow no light through
27.6 Shadows
Ray – Thin beam of light
Shadow – formed where light rays cannot reach
Umbra – a total shadow
Penumbra – a partial shadow
27.7 Polarization
Polarization – the aligning vibrations in a transverse wave, usually by filtering out waves of others directions
27.8 Polarized Light and 3-D Viewing